Interconnect structures with enhanced electromigration resistance

Abstract

Interconnect structures are provided that include an intermetallic compound as either a cap or liner material. The intermetallic compound is a thermal reaction product of a metal or metal alloy of an interconnect metallic region with a metal of either a metal cap or a metal layer. In some embodiments, the metal cap may include a metal nitride and thus a nitride-containing intermetallic compound can be formed. The formation of the intermetallic compound can improve the electromigration resistance of the interconnect structures and widen the process window for fabricating interconnect structures.

What is claimed is: 
     
       1. An interconnect structure comprising:
 at least one interconnect metallic region of an interconnect metal or metal alloy, M1, embedded in an opening located in an interconnect dielectric material layer, wherein a topmost surface of said at least one interconnect metallic region is coplanar with a topmost surface of said interconnect dielectric material layer; 
 a nitride-containing intermetallic compound containing cap located on said topmost surface of said at least one interconnect metallic region, wherein said nitride-containing intermetallic compound containing cap is a metal alloy including M1 and another metal, M3, and nitrogen, wherein M3 is different from M1; and 
 a dielectric capping layer located on exposed portions of said topmost surface of said interconnect dielectric material and on sidewall surfaces and a topmost surface of said nitride-containing intermetallic compound containing cap. 
 
     
     
       2. The interconnect structure of  claim 1 , wherein a diffusion barrier liner is present between said least one interconnect metallic region and said interconnect dielectric material layer. 
     
     
       3. The interconnect structure of  claim 1 , wherein M1 is selected from the group consisting of Cu, Al and Cu—Al. 
     
     
       4. The interconnect structure of  claim 1 , wherein M3 is Al, Hf, Mn, Co, Ru, Ir, Rh or W. 
     
     
       5. The interconnect structure of  claim 1 , wherein said nitride-containing intermetallic compound containing cap has a graded concentration of M1, wherein a content of M1 in said nitride-containing intermetallic compound containing cap is greatest at an interface formed between said nitride-containing intermetallic compound containing cap and said at least one interconnect metallic region, and decreases upwards to an interface formed between a topmost surface of said nitride-containing intermetallic compound containing cap and a surface of said dielectric capping layer. 
     
     
       6. The interconnect structure of  claim 1 , wherein said nitride-containing intermetallic compound containing cap has sidewall surfaces that are vertically aligned to sidewall surfaces of said at least one interconnect metallic region. 
     
     
       7. The interconnect structure of  claim 1 , wherein said dielectric capping layer comprises SiC, Si 4 NH 3 , SiO 2 , a carbon doped oxide, a nitrogen and hydrogen doped silicon carbide SiC(N,H) or multilayers thereof. 
     
     
       8. The interconnect structure of  claim 1 , wherein said nitrogen is present in said nitride-containing intermetallic compound containing cap in a content from 1 atomic percent to 75 atomic percent. 
     
     
       9. A method of forming an interconnect structure, said method comprising:
 forming at least one interconnect metallic region of an interconnect metal or metal alloy, M1, embedded in an opening located in an interconnect dielectric material layer, wherein a topmost surface of said at least one interconnect metallic region is coplanar with a topmost surface of said interconnect dielectric material layer; 
 depositing a non-selective metal layer of metal, M3, on said topmost surface of said at least one interconnect metallic region and on said topmost surface of said interconnect dielectric material layer, wherein M3 is different from M1; 
 first converting said metal layer into a metal nitride layer, M3-N; 
 second converting a portion of metal nitride layer that is located directly on said at least one interconnect metallic region into a nitride-containing intermetallic compound containing cap, wherein said nitride-containing intermetallic compound containing cap is a thermal reaction product of M1 and M3-N; 
 removing remaining portions of said metal nitride layer selective to said nitride-containing intermetallic compound containing cap; and 
 forming a dielectric capping layer on exposed portions of said topmost surface of said interconnect dielectric material and on sidewall surfaces and a topmost surface of said nitride-containing intermetallic compound containing cap. 
 
     
     
       10. The method of  claim 9 , wherein said first converting comprises a thermal nitridation process. 
     
     
       11. The method of  claim 9 , wherein first converting comprises a plasma nitridation process. 
     
     
       12. The method of  claim 9 , wherein said second converting comprises a thermal anneal. 
     
     
       13. The method of  claim 9 , wherein said second converting comprises a laser anneal. 
     
     
       14. The method of  claim 9 , wherein a content of M1 in said interconnect metallic region after said second converting is lower than a content of M1 in said interconnect metallic region prior to said first converting. 
     
     
       15. The method of  claim 9 , wherein M1 is selected from the group consisting of Cu, Al and Cu—Al. 
     
     
       16. The method of  claim 9 , wherein M3 is Al, Hf, Mn, Co, Ru, Ir, Rh or W. 
     
     
       17. The method of  claim 9 , wherein said nitride-containing intermetallic compound containing cap has a graded concentration of M1, wherein a content of M1 in said nitride-containing intermetallic compound containing cap is greatest at an interface formed between said nitride-containing intermetallic compound containing cap and said at least one interconnect metallic region, and decreases upwards from said interface. 
     
     
       18. The method of  claim 12 , wherein said thermal anneal is performed in a nitrogen-containing ambient and at a temperature from 100° C. to 400° C. 
     
     
       19. The method of  claim 13 , wherein said laser anneal is performed in a nitrogen-containing ambient and at a temperature from 400° C. to 800° C.